The development of communication infrastructures in recent years has allowed large volumes of moving image data to be transmitted and received through telephone lines, in addition to simple speech signals. In this case, in order to use from speech signals that can be transmitted even at a low bit rate to moving image data that needs to be transmitted at a high bit rate in the same framework and improve the efficiency of lines, for example, a variable bit rate transmission scheme is developed.
Also, in speech signal or audio signal coding, scalable coding techniques have been developed whereby it is possible to decode speech signals and audio signals from part of encoded information and suppress the degradation of sound quality even in a case where packet loss occurs (e.g. see Patent Document 1).
As a representative example of these scalable coding techniques, a method is disclosed for realizing scalability on the frequency axis by splitting an input signal in the frequency domain into the lower band component and the higher band component (and the middle band component) and encoding and transmitting the signal of each band (e.g. see Patent Document 2, Patent Document 3 and Patent Document 4).    Patent Document 1: Japanese Patent Application Laid-Open No. HEI10-97295    Patent Document 2: Japanese Patent Application Laid-Open No. 2005-114814    Patent Document 3: Japanese Patent Application Laid-Open No. 2006-189836    Patent Document 4: Japanese Patent Application Laid-Open No. 2006-119301